Optical control type microwave phase forming device

ABSTRACT

An optical control type microwave phase forming device includes: optical demultiplexers each for separating a light radiated from each of light sources into two branch lights; optical frequency converters each for deviating one of the two branch lights outputted from an optical demultiplexer by a predetermined frequency for outputting as a signal light; signal light emitting units each for converting the signal light into a signal light beam having a predetermined beam width to emit the signal light as a signal light beam to space; a spatial optical modulator for phase-modulating the signal light beams into signal light beams having a desired phase distribution; an optical multiplexer for converting the signal light beam outputted from the spatial optical modulator into a multiplex signal light beam to travel a coaxial optical path; an optical synthesizer for synthesizing the other branch lights outputted from the optical demultiplexers into a local light; a local light emitting unit for converting the local light into a light beam having a predetermined beam width to emit the light beam as a local light beam to space; and a beam synthesizer for spatially superimposing the signal light beam and the local light beam to form a synthesized beam.

TECHNICAL FIELD

The present invention relates to an optical control type microwave phaseforming device which can be applied to a multi-beam forming circuit foran array antenna for controlling, by using a light wave, a plurality ofmicrowave beams radiated from an array antenna.

BACKGROUND ART

In a conventional optical control type microwave phase forming device,the device is radiated with first and second beam lights, frequencies ofwhich are different from each other by a frequency of a microwavesignal. The first beam light is converted as a signal light beam into abeam light having a feed amplitude/phase distribution for each ofantenna elements of an array antenna by a spatial optical modulator, andthe signal light beam and the second beam light as a local light beamare spatially superimposed with each other, and spatially sampled. Thelight obtained through the sampling is then converted into microwavesignals through heterodyne detection by optoelectronic converters,respectively. Thereafter, the device is spatially radiated with themicrowave signals through the array antenna (refer to JP 7-202547 A(FIGS. 1 and 2), and JP 6-276017 A (FIG. 3), for example).

In the conventional optical control type microwave phase controllerdescribed in JP 7-202547 A, an amplitude/phase signal formed in each ofelements of a spatial optical modulator and a feed signal for each ofelements of an array antenna show one-to-one correspondence. As aresult, no more than one microwave phase wave surface can be formed byone spatial optical modulator, and hence there is a problem in that itis impossible to generate the feed signals for the array antenna forradiating a plurality of microwave beams.

In addition, FIG. 3 of JP6-276017A is concerned with multi-beamformation. However, in a construction shown in FIG. 3, directions of aplurality of beams are determined based on positions of masks,respectively. Therefore, a plurality of beams can not be directed in thesame direction or can not be superimposed, and hence there is a problemin that the directions of a plurality of beams are limited among themutual beams.

The present invention has been made in order to solve theabove-mentioned problems, and it is, therefore, an object of the presentinvention to obtain an optical control type microwave phase formingdevice which is capable of simultaneously forming a plurality ofmicrowave phase surfaces using one spatial optical modulator.

DISCLOSURE OF THE INVENTION

An optical control type microwave phase forming device according to thepresent invention includes: a first optical demultiplexer for branchinga light radiated from a first light source into two branch lights; asecond optical demultiplexer for branching a light radiated from asecond light source into two branch lights; a first optical frequencyconverter for deviating a frequency of one of the branch lightsoutputted from the first optical demultiplexer by a predeterminedfrequency based on a first microwave signal to output the resultantlight as a first signal light; and a second optical frequency converterfor deviating a frequency of one of the branch lights outputted from thesecond optical demultiplexer by a predetermined frequency based on asecond microwave signal to output the resultant light as a second signallight.

In addition, the optical control type microwave phase forming device ofthe present invention further includes: a first signal light emittingunit for converting the first signal light into a signal light beamhaving a predetermined beam width to emit the signal light as a firstsignal light beam to space; a second signal light emitting unit forconverting the second signal light into a signal light beam having apredetermined beam width to emit the signal light as a second signallight beam to space; a spatial optical modulator for phase-modulatingthe first and second signal light beams inputted to different areasthereof to convert the resultant signal light beams into signal lightbeams having respective desired spatial phase distributions; and anoptical multiplexer for converting the first and second signal lightbeams different in wavelength outputted from the spatial opticalmodulator into a multiplex signal light beam to travel a coaxial opticalpath.

Furthermore, the optical control type microwave phase forming deviceaccording to the present invention further includes: an opticalsynthesizer for synthesizing the other branch light outputted from thefirst optical demultiplexer and the other branch light outputted fromthe second optical demultiplexer into a local light; a local lightemitting unit for converting the local light into a light beam having apredetermined beam width to emit the light beam as a local light beam tospace; a beam synthesizer for spatially superimposing the first andsecond light beams outputted from the optical multiplexer and the locallight beam to form a synthetic beam; and a plurality of optoelectronicconverters for spatially sampling the synthetic beam to convert theresultant beam into microwave signals through heterodyne detection tooutput the microwave signals, respectively.

BRIEF DESCRIPTION OF THE DRWAINGS

FIG. 1 is a block diagram showing a construction of an optical controltype microwave phase forming device according to Embodiment 1 of thepresent invention;

FIG. 2 is a diagram showing a construction of an optical multiplexer ofthe optical control type microwave phase forming device according toEmbodiment 1 of the present invention;

FIG. 3 is a diagram showing a construction of an optical multiplexer ofthe optical control type microwave phase forming device according toEmbodiment 2 of the present invention;

FIG. 4 is a block diagram showing a construction of an optical controltype microwave phase forming device according to Embodiment 3 of thepresent invention;

FIG. 5 is a block diagram showing a construction of an optical controltype microwave phase forming device according to Embodiment 5 of thepresent invention;

FIG. 6 is a block diagram showing a construction of an optical controltype microwave phase forming device according to Embodiment 6 of thepresent invention; and

FIG. 7 is a block diagram showing a construction of an optical controltype microwave phase forming device according to Embodiment 7 of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will hereinafter be described basedon the accompanying drawings.

Embodiment 1

An optical control type microwave phase forming device according toEmbodiment 1 of the present invention will now be described withreference to the corresponding drawings. FIG. 1 is a block diagramshowing a construction of the optical control type microwave phaseforming device according to Embodiment 1 of the present invention. Notethat in the drawings, the same reference numerals designate the same orcorresponding constituent elements.

In FIG. 1, the optical control type microwave phase forming deviceaccording to the present invention includes: light sources 10 and 20;optical demultiplexers 12 and 22; optical frequency converters 13 and23; microwave signal input terminals 14 and 24; signal light emittingunits 15 and 25; a spatial optical modulator 30; a spatial opticalmodulator controller 31; an optical multiplexer 40; an opticalsynthesizer 50; a local light emitting unit 51; a beam synthesizer 52; alens array 53; an optical fiber array 54; optoelectronic converters 55;and microwave signal output terminals 56.

Next, an operation of the optical control type microwave phase formingdevice according to Embodiment 1 will be described with reference to thecorresponding drawings. FIG. 2 is a diagram showing a construction ofthe optical multiplexer of the optical control type microwave phaseforming device according to Embodiment 1.

As shown in FIG. 1, a light radiated from the light source 10 isbranched into two branch lights by the optical demultiplexer 12. Theoptical frequency converter 13 deviates a frequency of one of the branchlights by a predetermined frequency using a first microwave signalinputted through the microwave signal input terminal 14 to output theresultant light as a signal light 11. The signal light 11 having thefrequency obtained through the frequency deviation is converted into asignal light beam 11 having a predetermined beam width through thesignal light emitting unit 15 constituted of an optical fiber and a lensfor example, and the signal light beam 11 is then emitted to space. Thesignal light beam 11 emitted to space is then inputted to the spatialoptical modulator 30. As for an optical frequency converter fordeviating a frequency of a light, for example, an optical frequencyshifter utilizing an acousto-optic effect is commercialized.

Likewise, a light radiated from the light source 20 for radiating alight having a wavelength different from that of the light radiated fromthe light source 10 is branched into two branch lights by the opticaldemultiplexer 22. The optical frequency converter 23 deviates thefrequency of one of the branch lights by a predetermined frequency usinga second microwave signal inputted through the microwave signal inputterminal 24 to output the resultant light as a signal light 21. Thesignal light 21 having the frequency obtained through the frequencydeviation is converted into a signal light beam 21 having apredetermined beam width through the signal light emitting unit 25constituted of an optical fiber and a lens for example, and the signallight beam 21 is then inputted to an area on the spatial opticalmodulator 30 which is different from that for the signal light beam 11.

The signal light beam 11 and the signal light beam 21 which have beeninputted to the different areas on the spatial optical modulator 30 arespatially modulated with their phases in accordance with an input signalsent from the spatial optical modulator controller 31 to be outputted inthe form of signal light beams (output lights) 16 and 26 which areconverted so as to have respective desired spatial phase distributionsfrom the spatial optical modulator 30, respectively. Note that a liquidcrystal element, for example, is given as the spatial optical modulator30.

The signal light beams 16 and 26 outputted from the spatial opticalmodulator 30 are inputted to the optical multiplexer 40. The opticalmultiplexer 40 changes an optical path of an input signal light incorrespondence to a wavelength, an incident position, and an incidentangle of the input signal light. Thus, the optical multiplexer 40converts the signal light beams 16 and 26 which are different inincident position and wavelength into a multiplex signal light beam totravel through a coaxial optical path to output the resultant multiplexsignal light beam.

A function of the optical multiplexer 40 can be realized by utilizingthe dependency of an angle of refraction or an angle of reflection on awavelength in a wavelength dispersion element such as a prism or adiffraction grating. For example, as shown in FIG. 2, the opticalmultiplexer 40 can be constructed by combining two prisms 41 and 42 witheach other. Incident light beams (the signal light beams 16 and 26)which are different in wavelength and have been inputted to the prism 41are refracted at different angles in correspondence to their differentwavelengths, respectively, to be emitted at different angles from theprism 41. The prism 42 is disposed in a place where the two emittedlight beams intersect each other. The two emitted light beams are madeincident to the prism 42. An intersection is uniquely determined byangles of refraction of the two incident light beams depending on theincidence conditions and the wavelengths of the two incident lights tothe prism 41. Since the two lights which have been made incident atdifferent angles to the prism 42 are refracted at different angleswithin the prism 42 in correspondence to their wavelengths, the twolights can be converted into a multiplex output light beam to travelthrough one and the same optical path.

A signal light beam (multiplex light) 43 which has been obtained throughthe multiplexing to be emitted from the optical multiplexer 40 so as totravel the coaxial optical path is inputted to the optical fiber array54 through the beam synthesizer 52.

On the other hand, the other branch light 18 obtained by branching thelight radiated from the light source 10 in the optical demultiplexer 12,and the other branch light 28 obtained by branching the light radiatedfrom the light source 20 in the optical demultiplexer 22 are synthesizedin the form of a local light by the optical synthesizer 50. The locallight is then converted into a local light beam having a predeterminedbeam width through the local light emitting unit 51 constituted of anoptical fiber, a lens, and the like. The local light beam is thenspatially superimposed on the above-mentioned signal beam (multiplexlight) 43 through the beam synthesizer 52 to obtain a synthetic beamwhich is in turn inputted to the optical fiber array 54.

An incidence-end side of the optical fiber array 54 may be provided withthe lens array 53 in order to enhance a coupling efficiency of inputlights to the respective optical fibers constituting the optical fiberarray 54.

The lights which have been inputted to the respective optical fibers arepropagated through the respective optical fibers to be inputted to theoptoelectronic converters 55 connected to the optical fibers,respectively. The lights inputted to the respective optoelectronicconverters 55 are then converted into microwave signals through theheterodyne detection to be outputted through the respective microwavesignal output terminals 56. A phase distribution of each of themicrowave signals becomes a phase distribution given by the spatialoptical modulator 30.

In a case where the microwave signals are applied to an array antenna,the output signals outputted through the microwave signal outputterminals 56 are fed to respective antenna elements of the array antennathrough a microwave amplifier or the like as may be necessary to beradiated to space.

The microwave output signal outputted from a certain optoelectronicconverter 55 will hereinafter be described. The frequency of the lightsource 10 is assigned fo1, the frequency of the microwave signal isassigned fm1, and a phase modulation amount of light in the element ofthe spatial optical modulator 30 becoming the incident light to theoptical fiber to which attention is paid is assigned Φ1. Likewise, thefrequency of the light source 20 is assigned fo2, the frequency of themicrowave signal is assigned fm2, and a phase modulation amount of lightis assigned Φ2.

The light inputted to the optoelectronic converter 55 contains thefollowing four frequency components, assuming the amplitude of each ofwhich to be 1:

-   -   cos(2π(fo1+fm1)t+Φ1);    -   cos(2πfo1 t);    -   cos(2π(fo2+fm2)t+Φ2); and    -   cos(2πfo2 t).        A sum or difference between arbitrary two frequency components        of those frequency components is outputted from the        optoelectronic converter 55.

When a frequency difference in emitted light between the light source 10and the light source 20 is wider than a frequency band of theoptoelectronic converter 55, the frequency components of the microwavesignal outputted from the optoelectronic converter 55 are the followingtwo frequency components, and the phase modulation amounts Φ1 and Φ2 oflight given by the spatial optical modulator 30 are superimposed on thefrequency components of the microwave signal outputted from theoptoelectronic converter 55, respectively:

-   -   cos(2πfm1 t+Φ1); and    -   cos(2πfm2 t+Φ2).

As in Embodiment 1, the lights which are modulated with the phases Φ1and Φ2 in the different areas within the spatial optical modulator 30can be converted by the optical multiplexer 40 into the multiplex signalbeam to travel through one and the same optical path. Hence, the twolights and the microwave signals generated therefrom can be controlledindependently of one another.

Embodiment 2

An optical control type microwave phase forming device according toEmbodiment 2 of the present invention will hereinafter be described withreference to the corresponding drawing. FIG. 3 is a diagram showing aconstruction of an optical multiplexer of the optical control typemicrowave phase forming device according to Embodiment 2 of the presentinvention.

In Embodiment 1 described above, the example of the optical multiplexer40 constituted of the prisms 41 and 42 was shown. However, the functionof the optical multiplexer 40 can also be realized by utilizing thedependency of an angle of reflection on a wavelength in a wavelengthdispersion element such as a reflection type diffraction grating.

For example, the function of the optical multiplexer 40 can be realizedby combining two diffraction gratings 44 and 45 with each other as shownin FIG. 3. Incident lights (the signal light beams 16 and 26) havingdifferent wavelengths and made incident to the diffraction grating 44are reflected at different angles in correspondence to their wavelengthsand incident angles. The diffraction grating 45 is disposed in a placewhere the two reflected lights intersect each other. Thus, the tworeflected lights are made incident to the diffraction grating 45. Anintersection is uniquely determined from an angle of refractiondepending on the incidence conditions and the wavelengths of the twoincident lights to the diffraction grating 44. The two lights which havebeen made incident at different angles to the diffraction grating 45 arereflected at different angles by the diffraction grating 45 incorrespondence to their wavelengths. Hence, the reflected lights can beconverted into the multiplex signal light beam to travel through one andthe same optical path.

Such a function is not limited to a prism or a diffraction grating, andthus can be realized in the form of various constructions by utilizingthe dependency of a refraction or reflection direction on a wavelengthin an element having a wavelength dispersion property such as a photoniccrystal.

Embodiment 3

An optical control type microwave phase forming device according toEmbodiment 3 of the present invention will hereinafter be described withreference to the corresponding drawing. FIG. 4 is a block diagramshowing a construction of the optical control type microwave phaseforming device according to Embodiment 3 of the present invention.

In FIG. 4, the optical control type microwave phase forming deviceaccording to the present invention includes: the light sources 10 and20; the optical demultiplexers 12 and 22; the optical frequencyconverters 13 and 23; the microwave signal input terminals 14 and 24; anoptical synthesizer 46; a signal light emitting unit 47; an opticalbranching filter 49; the spatial optical modulator 30; the spatial lightmodulator controller 31; the optical multiplexer 40; the opticalsynthesizer 50; the local light emitting unit 51; the beam synthesizer52; the lens array 53; the optical fiber array 54; the optoelectronicconverters 55; and the microwave signal output terminals 56.

Next, an operation of the optical control type microwave phase formingdevice according to Embodiment 3 will be described with reference to thecorresponding drawing.

The signal lights 11 and 21 which have been changed in frequency afterbeing radiated from the light source 10 and the light source 20 aresynthesized by the optical synthesizer 46. A synthetic light 48 is thenconverted into a signal light beam having a predetermined beam widththrough the signal light emitting unit 47 to be inputted to the opticalbranching filter 49. The optical branching filter 49 outputs the inputlight from different places therein in correspondence to the wavelengthsof the input light. The optical branching filter 49 is equal to anelement which is obtained by changing input and output directions of theoptical multiplexer 40. Thus, the signal light beams 11 and 21 areoutputted from different places within the optical branching filter 49in correspondence to their wavelength bands. The signal light beams 11and 21 are inputted to different areas of the optical spatial modulator30. An operation after the above operation is the same as that inEmbodiment 1 described above.

The optical branching filter 49 can be realized, for example, based on aconstruction in which the light is inputted to the output side of theoptical multiplexer 40 shown in FIG. 2 or 3, and is outputted from theinput side thereof.

Application of the optical branching filter 49 to the input side of thespatial optical modulator 30 makes it possible to multiplex a pluralityof lights between the optical synthesizer 46 and the lens (signal lightemitting unit) 48. Thus, it is possible to reduce the number oftransmission lines and the number of input lenses for the spatialoptical modulator 30.

Embodiment 4

An optical control type microwave phase forming device according toEmbodiment 4 of the present invention will hereinafter be described.

In Embodiment 3 described above, the optical multiplexer 40 and theoptical branching filter 49 are disposed symmetrically with respect tothe spatial optical modulator 30. Thus, it is possible to eliminate thewavelength dependency on input and output directions and on places ofthe optical multiplexer 40 and the optical branching filter 49. Hence,even when the light sources having different wavelength bands are used,the optical multiplexer 40 and the optical branching filter 49 can copewith such a case without changing the disposition thereof.

In addition, also in a case where three or more light sources are usedto form three or more microwave phase wave surfaces, the sameconstruction in constituent elements in and after the opticalsynthesizer 46 as that of Embodiment 3 described above can be appliedthereto.

Embodiment 5

An optical control type microwave phase forming device according toEmbodiment 5 of the present invention will hereinafter be described withreference to the corresponding drawing. FIG. 5 is a block diagramshowing a construction of the optical control type microwave phaseforming device according to Embodiment 5 of the present invention.

In FIG. 5, the optical control type microwave phase forming deviceaccording to the present invention includes: the light sources 10 and20; the optical demultiplexers 12 and 22; the optical frequencyconverters 13 and 23; the microwave signal input terminals 14 and 24;the signal light emitting units 15 and 25; the spatial optical modulatorcontroller 31; a spatial optical modulator 35; the optical multiplexer40; a lens 60; the optical synthesizer 50; the local light emitting unit51; the beam synthesizer 52; the lens array 53; the optical fiber array54; the optoelectronic converters 55; and the microwave signal outputterminals 56.

The lens 60 is disposed between the spatial optical modulator 35 and theoptical fiber array 54. Also, the spatial optical modulator 35 isdisposed so that its output surface agrees in position with a front-sidefocal surface of the lens 60, and the optical fiber array 54 or the lensarray 53 is disposed so that its incidence end face agrees in positionwith a rear-side focal surface of the lens 60.

Next, an operation of the optical control type microwave phase formingdevice according to Embodiment 5 will be described with reference to thecorresponding drawing.

The spatial optical modulator 35 converts intensity distributions of thesignal lights 11 and 21 into intensity distributions of antennaradiation beams constituting a multi-beam, respectively. The lights 16and 26 obtained through the intensity distribution are converted,similarly to Embodiments 1 and 2 described above, with their opticalpaths by the optical multiplexer 40, and then pass through the lens 60.

Here, the output surface of the spatial optical modulator 35 and theincidence end face of the optical fiber array 54 have a relationship ofFourier transform through the lens 60. Thus, the optical signals whichare obtained by Fourier-transforming the output signals of the spatialoptical modulator 35 are inputted to the optical fibers of the opticalfiber array 54. Moreover, since the feed signal to the array antenna andthe antenna radiation pattern in a long distance have also arelationship of Fourier transform, the intensity distributions of theoutput lights from the spatial optical modulator 35 and the antennaradiation pattern show a nearly analogous relationship. For example,when the spatial modulator 35 is given a triangular intensitydistribution, the antenna radiation pattern becomes a triangleaccordingly.

Embodiment 6

An optical control type microwave phase forming device according toEmbodiment 6 of the present invention will hereinafter be described withreference to the corresponding drawing. FIG. 6 is a block diagramshowing a construction of the optical control type microwave phaseforming device according to Embodiment 6 of the present invention.

In FIG. 6, the optical control type microwave phase forming deviceaccording to the present invention includes: the light sources 10 and20; the optical demultiplexers 12 and 22; the optical frequencyconverters 13 and 23; the microwave signal input terminals 14 and 24;the optical synthesizer 46; the signal light emitting unit 47; theoptical branching filter 49; the spatial optical modulator controller31; the spatial optical modulator 35; the optical multiplexer 40; thelens 60; the optical synthesizer 50; the local light emitting unit 51;the beam synthesizer 52; the lens array 53; the optical fiber array 54;the optoelectronic converters 55; and the microwave signal outputterminals 56.

Next, an operation of the optical control type microwave phase formingdevice according to Embodiment 6 will be described with reference to thecorresponding drawing.

Similarly to Embodiment 3 described above, the lights which have beenradiated from the light source 10 and the light source 20 are inputtedto the different areas on the spatial optical modulator 35. The inputsignal lights 11 and 21 are intensity-modulated to be outputted by thespatial optical modulator 35 in correspondence to distributionscorresponding to desired antenna radiation patterns, respectively, tooperate similarly to the case of Embodiment 5 described above.

As a result, a plurality of lights can be multiplexed between theoptical synthesizer 46 and the lens (signal light emitting unit) 47.Thus, it is possible to reduce the number of transmission lines, and thenumber of input lenses for the spatial optical modulator 35.

Embodiment 7

An optical control type microwave phase forming device according toEmbodiment 7 of the present invention will hereinafter be described withreference to the corresponding drawing. FIG. 7 is a block diagramshowing a construction of the optical control type microwave phaseforming device according to Embodiment 7 of the present invention.

In FIG. 7, the optical control type microwave phase forming deviceaccording to the present invention includes: the light sources 10 and20; the optical demultiplexers 12 and 22; the optical frequencyconverters 13 and 23; the microwave signal input terminals 14 and 24;the optical synthesizer 46; the signal light emitting unit 47; theoptical branching filters 49; the spatial optical modulators 30; thespatial optical modulator controllers 31 and 32; the opticalmultiplexers 40; the optical synthesizer 50; the local light emittingunit 51; the beam synthesizer 52; the lens array 53; the optical fiberarray 54; the optoelectronic converters 55; and the microwave signaloutput terminals 56.

Next, an operation of the optical control type microwave phase formingdevice according to Embodiment 7 will be described with reference to thecorresponding drawing.

The branch lights 18 and 28 which have been radiated from the lightsources 10 and 20, respectively, are synthesized by the opticalsynthesizer 50, and a synthetic light is then radiated with apredetermined beam width to space from the lens (local light emittingunit) 51. By the optical branching filter 49, the radiated light isbranched into lights 19 and 29 having respective optical paths which aredifferent from each other in correspondence to their wavelengths. Theoutput lights 19 and 29 are then inputted to the input side of thespatial optical modulator 30.

The spatial intensity distributions of the output lights 19 and 29 areconverted into predetermined intensity distributions, respectively, andafter the intensity distribution conversion, the resultant lights areoutputted from the spatial optical modulator 30. The output lights areconverted into a multiplex signal light to travel through one and thesame optical path by the optical multiplexer 40. The multiplex signallight is then inputted to the optical fiber array 54 through the beamsynthesizer 52.

In addition to the phase distribution, the intensity distribution canalso be controlled, which results in enhancement of the reduction of theside lobe of the radiated beams from the array antennas, and theflexibility in the control or the like over the beam widths.

Embodiment 8

While in Embodiment 7 described above, the intensity modulation iscarried out for the branch lights 18 and 28, the spatial opticalmodulator 35 may be inserted in the spatial optical modulator 30 on anincidence side or an emission side thereof in order to carry out theintensity modulation of the branch lights 18 and 28.

Embodiment 9

While in each of Embodiments described above, two multi-beams aregenerated using the two light sources, it is to be understood that acircuit for forming three or more multi-beams can be realized usingthree or more light sources.

Embodiment 10

While each of Embodiments described above has been explained withrespect to the construction using the transmission type spatial opticalmodulator 30, it is to be understood that a reflection type spatialoptical modulator can also be applied.

Embodiment 11

While in each of Embodiments described above, the branch light 11 fromthe light source 10 is frequency-converted, the frequency of the otherbranch light 18 may be deviated. In addition, both of the frequencies ofthe branch light 11 and the branch light 18 may be converted.

Embodiment 12

While in each of Embodiments described above, one light source and thefrequency converter are used to form one microwave, two light sourcesmay also be used and the wavelengths of the light from the two lightsources may be controlled such that a frequency difference in lightbetween the two light sources becomes a desired microwave frequency.

Embodiment 13

While in each of Embodiments described above, after completion of thesampling of the light, the lights are transmitted to the optoelectronicconverters 55 through the optical fiber array 54, respectively, thelights may be directly applied to an array of the optoelectronicconverters 55 without through the optical fiber array 54.

INDUSTRIAL APPLICABILITY

The optical control type microwave phase forming device according to thepresent invention, as described above, can be applied to the multi-beamforming circuit for an array antenna. Thus, by using the opticalmultiplexer for multiplexing a plurality of lights different inwavelength band and a plurality of lights traveling through respectiveoptical paths, lights outputted from different areas on one spatialoptical modulator can be converted into a multiplex light signal totravel through one and the same optical path. Hence, a plurality ofmicrowave phase surfaces can be simultaneously formed by one spatialoptical modulator.

1. An optical control type microwave phase forming device, comprising: afirst optical demultiplexer for branching a light radiated from a firstlight source into two branch lights; a second optical demultiplexer forbranching a light radiated from a second light source into two branchlights; a first optical frequency converter for deviating a frequency ofone of the branch lights outputted from the first optical demultiplexerby a predetermined frequency based on a first microwave signal to outputthe resultant light as a first signal light; a second optical frequencyconverter for deviating a frequency of one of the branch lightsoutputted from the second optical demultiplexer by a predeterminedfrequency based on a second microwave signal to output the resultantlight as a second signal light; a first signal light emitting unit forconverting the first signal light into a signal light beam having apredetermined beam width to emit the signal light as a first signallight beam to space; a second signal light emitting unit for convertingthe second signal light into a signal light beam having a predeterminedbeam width to emit the signal light as a second signal light beam tospace; a spatial optical modulator for phase-modulating the first andsecond signal light beams inputted to different areas thereof to convertthe resultant signal light beams into signal light beams havingrespective desired spatial phase distributions; an optical multiplexerfor converting the first and second signal light beams different inwavelength outputted from the spatial optical modulator into a multiplexsignal light beam to travel a coaxial optical path; an opticalsynthesizer for synthesizing the other branch light outputted from thefirst optical demultiplexer and the other branch light outputted fromthe second optical demultiplexer into a local light; a local lightemitting unit for converting the local light into a light beam having apredetermined beam width to emit the light beam as a local light beam tospace; a beam synthesizer for spatially superimposing the first andsecond light beams outputted from the optical multiplexer, and the locallight beam to form a synthetic beam; and a plurality of optoelectronicconverters for spatially sampling the synthetic beam to convert theresultant beam into microwave signals through heterodyne detection tooutput the microwave signals, respectively.
 2. An optical control typemicrowave phase forming device according to claim 1, wherein the spatialoptical modulator intensity-modulates the first and second signal lightbeams to convert the resultant signal light beams into signal lightbeams having respective desired spatial intensity distributions insteadof phase-modulating the first and second signal light beams to convertthe resultant signal light beams into signal light beams havingrespective desired spatial phase distributions, the optical control typemicrowave phase forming device further comprising: an optical fiberarray for transmitting the synthetic beam outputted from the beamsynthesizer to the plurality of optoelectronic converters; and a lensfor Fourier-transforming the first and second signal light beamsoutputted from the spatial optical modulator, the lens being disposed sothat its front-side focal surface agrees in position with an outputsurface of the spatial optical modulator, and its rear-side focalsurface agrees in position with an incidence end face of the opticalfiber array.
 3. An optical control type microwave phase forming device,comprising: a first optical demultiplexer for branching a light radiatedfrom a first light source into two branch lights; a second opticaldemultiplexer for branching a light radiated from a second light sourceinto two branch lights; a first optical frequency converter fordeviating a frequency of one of the branch lights outputted from thefirst optical demultiplexer by a predetermined frequency based on afirst microwave signal to output the resultant light as a first signallight; a second optical frequency converter for deviating a frequency ofone of the branch lights outputted from the second optical demultiplexerby a predetermined frequency based on a second microwave signal tooutput the resultant light as a second signal light; a first opticalsynthesizer for synthesizing the first and second signal lights; asignal light emitting unit for converting the synthetic light outputtedfrom the first optical synthesizer into a signal light beam having apredetermined beam width to emit the signal light as a synthetic signallight beam to space; an optical branching filter for spatiallyseparating the synthetic signal beam in correspondence to a wavelengthband of the synthetic signal light to output first and second signallight beams obtained through the spatial separation; a spatial opticalmodulator for phase-modulating the first and second signal light beamsinputted to different areas thereof to convert the resultant signallight beams into signal light beams having respective desired spatialphase distributions; an optical multiplexer for converting the first andsecond signal light beams different in wavelength outputted from thespatial optical modulator into a multiplex signal light beam to travel acoaxial optical path; a second optical synthesizer for synthesizing theother branch light outputted from the first optical demultiplexer andthe other branch light outputted from the second optical demultiplexerinto a local light; a local light emitting unit for converting the locallight into a light beam having a predetermined beam width to emit thelight beam as a local light beam to space; a beam synthesizer forspatially superimposing the first and second light beams outputted fromthe optical multiplexer and the local light beam to form a syntheticbeam; and a plurality of optoelectronic converters for spatiallysampling the synthetic beam to convert the resultant beam into microwavesignals through heterodyne detection to output the microwave signals,respectively.
 4. An optical control type microwave phase forming deviceaccording to claim 3, wherein the optical branching filter and theoptical multiplexer are disposed symmetrically with respect to thespatial optical modulator.
 5. An optical control type microwave phaseforming device according to claim 3, wherein the spatial opticalmodulator intensity-modulates the first and second signal light beams toconvert the resultant signal light beams into signal light beams havingrespective desired spatial intensity distributions instead ofphase-modulating the first and second signal light beams to convert theresultant signal light beams into signal light beams having respectivedesired spatial phase distributions, the optical control type microwavephase forming device further comprising: an optical fiber array fortransmitting the synthetic beam outputted from the beam synthesizer tothe plurality of optoelectronic converters; and a lens forFourier-transforming the first and second signal light beams outputtedfrom the spatial optical modulator, the lens being disposed so that itsfront-side focal surface agrees in position with an output surface ofthe spatial optical modulator, and its rear-side focal surface agrees inposition with an incidence end face of the optical fiber array.
 6. Anoptical control type microwave phase forming device according to claim3, further comprising: a second optical branching filter for spatiallyseparating the local light beam in correspondence to a wavelength bandof the local light beam to output first and second local light beamsobtained through the spatial separation; a second spatial modulator forphase-modulating the first and second local light beams inputted todifferent areas thereof to convert the resultant light beams into lightbeams having respective desired spatial phase distributions; and asecond optical multiplexer for converting first and second local lightbeams different in wavelength outputted from the spatial opticalmodulator into a multiplex light beam to travel through a coaxialoptical path, wherein the beam synthesizer spatially superimposes thefirst and second signal light beams outputted from the opticalmultiplexer, and the first and second local light beams outputted fromthe second optical multiplexer to form a synthetic beam, instead ofspatially superimposing the first and second signal light beamsoutputted from the optical multiplexer and the local light beam.